Known as conventional printers are electrophotographic printers, mimeograph printers, and the like.
In the electrophotographic printer, the whole surface of a clean drum is electrically charged by corona discharge, and the electrically charged drum surface is selectively exposed to light. The exposed surface is discharged, whereby a latent image can be formed on the drum surface by a charged area and an uncharged area. After the latent image is formed, toner is attached to the drum surface by a developing section, so as to form a visual image. Thus formed visual image is transferred onto a recording medium in a transfer section, and then is fixated to the recording medium by a fixating section.
Since the electrophotographic printer necessitates a process of forming a latent image per sheet at the time of printing a plurality of sheets, however, there is a limit to increasing the printing speed.
In the mimeograph printer, which is known as a light-duty printer for business use, on the other hand, a thermal head selectively forms holes in a stencil, so as to form a printing plate. Thus formed plate is wound about a drum, and then ink is supplied to the plate from the inside of the drum, whereby an ink image is formed by the ink passed through the above-mentioned holes. Thereafter, the ink image is transferred to a recording medium in a transfer section.
The mimeograph printer, however, has the following drawbacks. Namely, the plate wound about the drum has to be discarded after the printing is over. As a consequence, it is necessary to provide a mechanism for removing the plate to be discarded from the drum, a space for storing thus removed plate carrying ink, and a complicated mechanism for taking the plate out of the apparatus. Since ink attaches to the plate to be discarded, the amount of use of ink unnecessarily increases, thereby raising the cost of prints. Further, since no new image can be formed on a mimeograph stencil which has once been prepared, a new mimeograph stencil is necessary for forming a new plate. Thus, it is disadvantageous in that, while the running cost per sheet at the time of copy-printing a large number of sheets becomes lower, the running cost per sheet at the time of copy-printing a small number of sheets becomes higher. Also, since processes of discarding the used stencil, forming a new plate, winding the plate about a drum, and so forth are necessary for printing a new image, it is disadvantageous in that the apparatus complicates its structure and enhances its dimensions.